Examination of affiliation relations between hospitals and medical schools provides an opportunity to study the development of cooperation between organizations with similar goals but with different priorities assigned to these goals. Based on several theories of organizations, hypotheses are proposed concerning the probability that a medical school and a hospital will develop affiliation relations and the nature of such relations given different environmental conditions. To test the hypotheses, data will be collected at each of the six medical schools and 122 hospitals in the Philadelphia S.M.S.A. The study will be conducted in four phases: 1) Interviews with administrative personnel at each of the six medical schools; 2) Case studies of two hospitals affiliated with each of the medical schools; 3) Survey of administrators and selected chiefs of services at the 116 hospitals not included in the case studies; and 4) Use of existing data regarding inter-hospital ties and individual hospital characteristics. Analysis will focus on developing models of affiliation relations and relating these to the independent variables. The study will provide an empirical test of the validity of aspects of several of the prominent theories of organizational relations, and will contribute to the methodologies available to organizational and medical sociologists. Information regarding the nature of these relationships can be used to develop public policy strategies to promote the rational development of affiliation agreements.